Change font inside document to specific point size

Question

Although this question has a duplicate flavor to it, the question that allegedly provides the solution, LaTeX -- specify font point size?, is hard to use since neither the question nor the answer contains a MWE or any code snippet at all to demonstrate the effect. The answer is also according to comments incomplete with respect to the necessary macros to include.

So I'll ask again. I need to set my tables in a 9pt font, whereas the document text should be in a 12pt font, and the document should throughout be double spaced. How?

\documentclass[12pt]{article}
\usepackage{setspace,lipsum}
    \doublespacing
\begin{document}
\lipsum[2]

\begin{tabular}{*3{l}} % <- this table should be set in 9pt
    Word & Word & Word\\
    Word & Word & Word\\
    Word & Word & Word\\
\end{tabular}

\lipsum[2]
\end{document}

I would have thought there was a package for something as fundamental as this?

---

EDIT

The example above was intended to be as minimal as possible (so that it's helpful to other people who find this question - I am always bothered by finding questions that are so unnecessarily specific and complicated that I'm not able to use it for my own document).

So what I really need this for is for floating tables (the caption should have 12pt as the document text). Below is such a MWE. The output does not, for some reason, have double spacing in the table.

\documentclass[12pt]{article}
\usepackage{setspace,lipsum}
    \doublespacing
\usepackage[justification=centering, font=normalsize, labelfont=bf]{caption}

\begin{document}
\lipsum[2]

\begin{table}
\centering\fontsize{9}{11}\selectfont
\begin{tabular}{*3{l}}
    Word & Word & Word\\
    Word & Word & Word\\
    Word & Word & Word\\
\end{tabular}
\caption{My table}
\end{table}

\lipsum[2]
\end{document}

Answer 1

Just tell LaTeX to use nine point type.

\documentclass[12pt]{article}
\usepackage{setspace,lipsum}
    \doublespacing
\begin{document}
\lipsum[2]

\begin{center}\setstretch{1}\fontsize{9}{11}\selectfont
\begin{tabular}{*3{l}} % <- this table should be set in 9pt
    Word & Word & Word\\
    Word & Word & Word\\
    Word & Word & Word\\
\end{tabular}
\end{center}

\lipsum[2]
\end{document}

For a really awful result, here's what you want:

\documentclass[12pt]{article}
\usepackage{setspace,lipsum}
    \doublespacing
\begin{document}
\lipsum[2]

{\strut\fontsize{9}{11}\selectfont
\begin{tabular}[t]{*3{l}} % <- this table should be set in 9pt
    Word & Word & Word\\
    Word & Word & Word\\
    Word & Word & Word\\
\end{tabular}}

\strut\lipsum[2]
\end{document}

The fact that in a table environment the interline spacing is reset to single spacing is a precise choice made by the setspace package. You can revert it by removing the setting the package does.

\documentclass[12pt]{article}
\usepackage{setspace,lipsum}
\usepackage[justification=centering, font=normalsize, labelfont=bf]{caption}

\makeatletter
\let\@xfloat\latex@xfloat % remove the redefinition made by setspace
\makeatother

\doublespacing

\begin{document}
\lipsum[2]

\begin{table}
\centering\fontsize{9}{11}\selectfont
\begin{tabular}{*3{l}}
    Word & Word & Word\\
    Word & Word & Word\\
    Word & Word & Word\\
\end{tabular}
\caption{My table}
\end{table}

\lipsum[2]
\end{document}

Answer 2

I read the plural form of 'table' in the OP. So, "stealing" @egregs solution I generalized:

\documentclass[12pt]{article}
\usepackage{setspace,lipsum}
  \doublespacing
\usepackage{etoolbox}
\preto\tabular{\fontsize{9}{11}\selectfont}

\begin{document}
%all tables should be set in 9pt now
\lipsum[2]

\medskip
\begin{tabular}{*3{l}}% <- especially this one
    Word & Word & Word\\
    Word & Word & Word\\
    Word & Word & Word\\
\end{tabular}
\medskip

\lipsum[2]
\end{document}